1. → need to guide UV light into gap; also beware temp effects
Birmingham Update
UV gluing study, following DESY-Berlin procedure (Simon and Sam)
Good progress in gluing and UV curing ASICs to hybrids.
So try using UV glue (Loctite 3525) to attach hybrid to sensor.
use Al bar with array of 10 UV diodes system as developed and constructed by Dennis
But bar soon becomes very hot.
Also difficult for UV light from diode to find its way into gap between hybrid and sensor; UV glue did not cure.
→ need to guide UV light into gap; also beware temp effects
27th April 2015:
10 chip bar at ~35V with 0.35A current limit (running on bench surface with no attempt at cooling)
WP3; 7 May 2015; John Wilson. 1

2. UV light guide diagram S Pyatt
Panel mount UV LEDs mounted into light guide
UVT Acrylic light guide
Coated with reflective paint
ASIC
ASIC/Hybrid UV glue
Hybrid
Hybrid/Sensor UV glue
PSU
Stand. Doubles as a heat sink. Straddles Hybrid/Sensor vacuum plate
WP3; 7 May 2015; John Wilson.

3. 3 hybrids glued using the 3 different UV glues and patterned glass ASIC for bonding trials (Simon and Sam)
Results below.
(No problem with UV curing – worked well for ASIC to hybrids).
Next: Simon setting up bonding tests + Sam measuring glue heights
ASIC Jig was kept the same for all 3 gluings.
Loctite 3525
Most viscous glue; the dots have kept their shape and locations well.
WP3; 7 May 2015; John Wilson.

4. Dymax 6 621
Smaller dots to the right hand side of hybrid are due to the height of glue needle on dispense master not being set perfectly so glue didn’t dispense correctly.
Some merging of the glue dots can be seen due to the low viscosity of the glue.
WP3; 7 May 2015; John Wilson.

5. Dymax 3013
Same issue here with needle height creating smaller dots to the right hand side
“Shadows” can be seen, and dots in strange locations due to the glue being so runny. Glue moves (like a rain drop down a window) across the pad before the ASIC is placed.
Glue dot placed
Glue dot “slides”
Because of the “slide” less glue is in the main dot, so there is less contact area at the correct height so there is less contact with the ASIC
WP3; 7 May 2015; John Wilson.

6. Birmingham Update Metrology (Sam)
Sam measured same panel many times (a la Bart) to check consistency . Measurements repeatable at ±1.5μm level
Same hybrid measured 10 times.
Graph on left shows the height of each of the ASIC pads below surface height for each of the 10 runs
Graph on right shows the average for each of the 10 pads, the error bar is the standard deviation.
WP3; 7 May 2015; John Wilson.

7. Birmingham Update DAQ (Juergen and Andy Chisholm)
Able to power up two hybrids at a time (250nm from 2013):
Stave09 power adapter from Ashley
+ have 2nd LVDS driver board already.
2nd VMOD-IB via Peter to be brought back from DESY
1st PC (in cleanroom) reverted to HSIO test system with our 250nm hybrid but set up to connect Atlys easily (on 3rd ethernet port).
2nd PC (outside cleanroom) fully set up with ITSDAQ/SCTDAQ with Atlys connected – easier access.
WP3; 7 May 2015; John Wilson.

8. Birmingham Update (contd)
Irradiation of ATLAS mini-sensors at Bham cyclotron
Till now, bare sensors have been irradiated
Problem: heating in intense bean but, after improvements, sensor temp remains below -10C. Annealing in beam should not now be a factor.
But still not proven that Bham irradiated sensors have usual behaviour a la Karlsruhe/KEK etc.
Irradiate with sensors, biased and bare: look for difference. (Copy Karlsruhe and compare).
Entering a phase where sensors are bonded and biased.
WP3; 7 May 2015; John Wilson. 8